664640213 has 4 divisors (see below), whose sum is σ = 682603500. Its totient is φ = 646676928.

The previous prime is 664640209. The next prime is 664640227. The reversal of 664640213 is 312046466.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 502790929 + 161849284 = 22423^2 + 12722^2 .

It is a cyclic number.

It is not a de Polignac number, because 664640213 - 2² = 664640209 is a prime.

It is a super-2 number, since 2×664640213² = 883493225473370738, which contains 22 as substring.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 664640213.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (664640203) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 8981588 + ... + 8981661.

It is an arithmetic number, because the mean of its divisors is an integer number (170650875).

Almost surely, 2^664640213 is an apocalyptic number.

It is an amenable number.

664640213 is a deficient number, since it is larger than the sum of its proper divisors (17963287).

664640213 is a wasteful number, since it uses less digits than its factorization.

664640213 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 17963286.

The product of its (nonzero) digits is 20736, while the sum is 32.

The square root of 664640213 is about 25780.6170019261. The cubic root of 664640213 is about 872.6944312081.

Adding to 664640213 its reverse (312046466), we get a palindrome (976686679).

The spelling of 664640213 in words is "six hundred sixty-four million, six hundred forty thousand, two hundred thirteen".